Mrs. Frisby and the Rats of NIMH is a 1971 children's science fiction/fantasy book by Robert C. O'Brien, with illustrations by Zena Bernstein. The novel was published by the New York City publishing house Atheneum Books.
This book was the winner of numerous awards including the 1972 Newbery Medal. Ten years following its publication, the story was adapted for film as The Secret of NIMH (1982).
The novel centers around a colony of escaped lab rats–the rats of NIMH–who live in a technologically sophisticated and literate society mimicking that of humans. They come to the aid of Mrs. Frisby, a widowed field mouse who seeks to protect her children and home from destruction by a farmer's plow.
The rats of NIMH were inspired by the research of John B. Calhoun on mouse and rat population dynamics at the National Institute of Mental Health from the 1940s to the 1960s.
After O'Brien's death in 1973, his daughter Jane Leslie Conly wrote two sequels to Mrs. Frisby and the Rats of NIMH.
Plot summary
Mrs. Frisby, a recently widowed mouse, lives with her four children in a cinder block, in a field belonging to a farmer named Mr. Fitzgibbon. Her son Timothy falls ill with pneumonia just as the farmer begins planning for spring plowing, which will destroy their home. Normally, the family would move to their summer home to avoid being uprooted, but Timothy is too ill to move. An older mouse named Mr. Ages, who was a friend of Mrs. Frisby's late husband Jonathan, gives her some medicine for Timothy. On her way home, she saves the life of a young crow named Jeremy from the farmer's cat, Dragon. In return, Jeremy flies Mrs. Frisby to an owl's tree so that she can ask for help moving her family. When the owl finds out that Mrs. Frisby is the widow of his old friend Jonathan, he suggests that she seek help from the rats who live in a rosebush on the farm.
Frisby discovers that the rats have a literate and mechanized society. They have technology such as elevators, have tapped the electricity grid to provide lighting and heating, and have acquired other human skills, such as storing food for the winter. Their leader, Nicodemus, tells Frisby of the rats' capture by scientists working for a laboratory located at the National Institute of Mental Health (NIMH) and the experiments that were performed on the rats, which increased the rats' intelligence to the point of being able to read, write and operate complicated machines, as well as enhancing their longevity and strength. Their increased intelligence and strength allowed them to escape from NIMH and migrate to their present location on the farm. Jonathan and Ages were the only two survivors of a group of eight mice who had been part of the experiments at NIMH and made the rats' escape possible.
Out of respect for Jonathan, the rats agree to move Frisby's house to a location safe from the plow. Nicodemus also tells Frisby that the rats have recently decided to abandon their lifestyle of dependence on humans, which some rats regard as theft. Instead, the rats aim to live independently. A group of rats, led by one named Jenner, rejected this plan and left the nest at some point before Frisby's arrival.
In order for the rats to move the Frisby home, the cat Dragon must be drugged, but the rats are too big to be able to do so. Mrs. Frisby volunteers to go, even though she learns that Jonathan was killed by Dragon while attempting to drug him. She is caught by the farmer's son, Billy, who puts her in a birdcage. While captured, Frisby overhears the farmer and his family discussing an incident at a nearby hardware store in which a group of rats was electrocuted after seemingly attempting to steal a small motor. This has attracted the attention of a group of men who have offered to exterminate the rats on the farmer's land free of charge. At night, the rat Justin comes to save Frisby and manages to get her out of the cage. The rats manage to move the Frisby house out of the way of the plow using a pulley and scaffolding system.